2006 Issue

www.utahengineerscouncil.org 30 UEC JOURNAL February 2006 vided the best solution for this high wall application. The geo-grid extends 35 feet behind the wall and the fabric layers were spaced at 1.5-foot centers vertically. The backfill for the wall was selected and placed carefully. We required that the fill be placed in 6-inch lifts and compacted to 98% of maximum dry density. The concrete fascia wall was 12 inches thick and reinforced with two curtains of rebar that was mostly used to counter the effects of temperature differentials and shrinkage. The fascia wall was designed to resist a small amount of non-accumu- lating lateral earth pressures. These pres- sures were the result of backfill not well confined within the geo-grid fabric be- tween layers. During construction the fascia wall progressed ahead of the MSE backfill by 8 feet. This allowed the fascia wall to be re- aligned continuously and provided a sur- face to compact against. The fascia wall was anchored into the MSE with galva- nized steel rods inserted as the backfill pro- gressed. A minimal footing under the fas- cia wall was used to support the dead weight of the wall. The designers worked with Staker Parson Ready Mix to provide a concrete mix design that achieved a crack-free wall over the entire surface. Concrete was designed with a very low slump/high mobility, aggregate gradation to mini- mize voids and maximize density, and a low water/cement ratio. The walls vertical alignment has not changed since it was placed into full op- eration. Trucks weighing over 110 ton and loaded with 60 ton of rock back into (and bump) the wall all day long with no signs of distress or movement. ■ Gravel Pit — continued ▲ Placing Geo-grid Wall Construction Complete: Gyratory Frame Under Construction in the Foreground. STRUCTURAL ENGINEERS ASSOCIATION OF UTAH SOCIETY FORUM